diff --git a/requirements.txt b/requirements.txt
index 6dc0ba1..725760b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 absl-py~=1.0.0
-attrs>=21.2.0
+attrs~=21.2.0
 dm-tree~=0.1.1
 matplotlib~=3.3.4
 mpmath
diff --git a/setup.py b/setup.py
index 9488908..2d6cec9 100644
--- a/setup.py
+++ b/setup.py
@@ -28,7 +28,7 @@ setup(
     license='Apache-2.0',
     install_requires=[
         'absl-py~=1.0.0',
-        'attrs>=21.2.0',
+        'attrs~=21.2.0',
         'dm-tree~=0.1.1',
         'matplotlib~=3.3.4',
         'scipy>=0.17',